Crystallographic shear planes, role

Role of Ciystallographic Shear Planes This area is tied to the subject of surface oxidation state. In redox kinetics it is believed that sites for hydrocarbon oxidation are different from that for reoxidation, and crystallographic shear planes (CSP) have been suggested to assist bulk oxygen movement between the sites 44,45,46,47), There have been a few studies of this phenomenon. In WO2.95 WO2.9 it has been shown CSPs are involved in oxygen transfer but... 

Most of our discussion will be confined to point defects in ionic solids (ceramics). Line defects, commonly referred to as dislocations, are characterized by displacements in the periodic structure of the lattice in certain directions. They play their most important role in the plastic deformation of metals. Planar defects include free surfaces, grain boundaries, stacking faults, and crystallographic shear planes. 

Crystallographic shear is an elegant structural transformation mechanism in oxides. We now address one of the most fundamental issues in heterogeneous catalysis by oxides the formation and the role of CS planes in oxidation catalysis. 

Erom the preceding discussion, the distinction between misfit defects shear domains formed by pure shear and CS planes formed by the elimination of anion vacancies in a specific crystallographic plane by shear and the collapse of the oxide lattice on that plane can be understood. This distinction between defects is central to catalytic reaction mechanisms in oxides. However, it is often not made in the literature on oxide catalysis and solid state oxide chemistry. This can result in an incorrect interpretation of observed data and of the role played by lattice oxygen atoms in catalytic reactions. The former are regions containing... 

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